1. Field of the Invention
This invention relates to a camera of the type in which a flash device is used, and more particularly, to a built-in flash camera or a camera with an external flash device of the type in which the flash device is automatically flashed when it is determined on the basis of the output of a photometry circuit of the camera that flashing of the flash device ensures a correct exposure, as with a dark or back lighted scene, and in which flashing of the flash device is prohibited when it is determined that flashing of the flash device is not necessary, as with an outdoor scene in the daytime.
2. Description of the Related Art
Various types of built-in flash cameras or cameras with an external flash device of the type in which the flash device is automatically flashed when it is determined at a photometry stage that the scene is dark or back lighted have been proposed recently.
In such cameras, charging of the flash device may be started after it has been determined that the scene is dark or back lighted. In that case, operation of a shutter release button has to be delayed until the charging of the flash device is completed, making it impossible for a photographer to take a picture immediately. In order to eliminate this shortcoming, a camera of the type in which waiting for the charging of the flash device is eliminated by automatically starting charging of the flash device for the next picture immediately after a picture has been taken has been proposed.
In the conventional camera of the above-described type, the flash is continuously charged until the voltage of the flash reaches a predetermined value required for flashing in a state where no monitoring is performed, charging being stopped when the voltage has reached the predetermined value. In consequence, in a case where a battery has been used up and the voltage of the battery is too low to charge the flash, charging of the flash may not be completed for a long period of time, during which time the booster circuit for the flash is continuously operated, causing heating of the component of the booster circuit, such as a transistor or a coil.
In that case, if use of the battery is stopped for a while, the voltage may recover by virtue of the characteristics of the battery, making it possible for the flash to be charged by that battery. However, in a case where the battery is used for a long period of time, it is often used up to such a degree that recovery thereof is impossible.
Furthermore, in the above-described type of camera, when the flash has been charged to a voltage sufficient for flashing, charging is stopped instantly.
However, after charging, the capacitor for the flash leaks gradually, thereby gradually reducing the charged voltage.
In consequence, the voltage may drop to a value too low for flashing by the time the next picture is taken. In that case, supplementary charging has to be performed immediately before the picture is taken, and operation of the shutter release button has to be meanwhile delayed.